Let's not make this more difficult (or expensive) than it needs to be.
Rate: I work for the amount you would pay an employee to perform the same function or task. I'm a big fan of a value-for-value exchange, so let's be fair with each other.
Liability: I obviously don't have a full-time job, so I cannot afford to assume the financial risk of your business. I could do the whole independent contractor thing but I've been a consultant and that only works out for the insurance brokers and carriers. I prefer to work under a countersigned offer of temporary employment and be covered under your existing liability policies. No fringe benefits. No expectation of full time employment. Just add me to the payroll, we split the witholdings and you give me the boot when I'm no longer needed. Easy-peasy.
Termination: Just say, "We no longer need your services," but a day or two notice would be appreciated. I am happy to discuss a reciprocal termination notice that helps you manage your risk.
24/7. The kids (2) are away at college and my bride, a high school French Teacher for 30 years, deserves some "me time."